This research aims to ease the critical shortage of pediatric rheumatologists by using decision support software to improve the ability of generalist physicians to make rheumatologic diagnoses. In our SBIR1 ?Empowering Physicians with Evidence-Based Decision Support for Pediatric Rheumatology? rheumatology information was added to the SimulConsult diagnostic decision support tool. Testing using pediatric rheumatology case vignettes showed that all groups of clinicians were more effective in diagnosis after using the tool. Diagnostic error was reduced, with error defined as the absence of the correct diagnosis or its category in the differential diagnosis. Error fell from 28% to 15% (45% relative reduction), with largest reductions among junior physicians (69% relative reduction) and Emergency Medicine physicians (62% relative reduction). This SBIR2 proposal extends the SBIR1 research to actual clinical practice, after improving the diagnostic tool in ways suggested by the SBIR1. We hypothesize improvements in actual practice similar to those using case vignettes. Wide use of such capabilities would ease the critical shortage of pediatric rheumatologists, and reduce instances of bad outcomes from delay or mistreatment. Aim 1 is to improve the decision support in ways suggested by a case-based quality improvement methodology developed using the 8 cases tested in the SBIR1. That methodology will be formalized to guide further improvement, using 100 additional cases. Improvements already surfaced using this methodology will be implemented, including a new dimension to specifying time, speed of emergence of a disease. Other improvements will be resources to assist non-specialists in identification of key findings, ?bundles? of several results of one test that can be combined to better represent the usefulness of obtaining that test, addition of further findings often not mentioned in narrative resources such as responses to particular treatments, adding exclusionary findings, and adding further diseases in the differential diagnosis of rheumatologic conditions. Aim 2 is a trial of effectiveness in clinical care. This will be done in the emergency department of Boston Children's Hospital, with ~500 patients over 12 months, and in rheumatology clinic at the hospital, with ~500 patients, for a total of 1000 cases. Cases will be randomized to a Control condition, in which the tester may use all usual resources such as textbooks or web searches, or an Intervention condition, in which the diagnostic tool is used and the same usual resources may be used, as well. Trainees will record their differential diagnosis and planned workup before and after the trial. These lists will be compared to the ?gold standard? diagnosis and workup, based on assessments of senior rheumatologists, lab testing and follow-up in subsequent months. Error, relevance, comprehensiveness, and cost impact, will be analyzed. Demonstrating that non-rheumatologists and trainees improve their diagnoses in pediatric rheumatology and save costs will enable the diagnostic decision support to be commercialized to hospitals and pediatricians.